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Geological Sciences.

The Mineralogy of Sand From Glacial Deposits of the Lake Michigan Lobe, Southwestern Michigan. Edward Hansen and Keiko Kito, Hope College, Department of Geological and Environmental Sciences, Holland, MI 49423

We investigated the mineralogy of sand size fractions of 10 till and 2 outwash samples from the Lake Border, Valparaiso and Whitehall moraines of the Lake Michigan Lobe. The sand size fractions were separated by wet sieving. Grain mounts were made of the 355, 250, 125 and 88 micron size fractions and the mineralogy of 300 grains in each mount was determined by qualitative electron microprobe analyses. Quartz dominates all sizes but proportions of carbonate and feldspar increase with decreasing grain size. This probably represents differential resistance to abrasion. Proportions of quartz, oxides, garnets, ferromagnesian silicates, feldspars and carbonates are very similar in till samples from the different moraines and from different places within the same moraine. Ratios of plagioclase to K-feldspar may vary systematically between and within moraines but needs to be confirmed by more extensive analysis. Finer-grained fractions of dune and beach sand are often enriched in oxides, garnets and ferromagnesian silicates compared to coarser grained fractions. Such enrichment is not evident in the till but occurs in some outwash samples. This suggests selective winnowing of less dense grains from the finer grained fraction may have been an important process during post glacial transport.

Origin of Pinstripes in Lake Michigan Coastal Dunes. Anna Davis and Kristen McPhee, Hope College, Department of Geological and Environmental Sciences, Holland, MI 49423

Pinstripes are thin layers of fine-grain sand in dune deposits. In dunes along the southeastern Lake Michigan coast fine-grain sand is often enriched in oxides, garnets and ferromagnesian silicates giving pinstripes a dark color. Hundreds of pinstripes, spaced from 0.01 to 1 meter apart, are exposed on the stoss slopes of some large parabolic dunes after scouring by strong winds. Pinstripe orientations indicate that they originally formed on lee slopes of actively migrating parabolic dunes. Debates on the origin of pinstripes generally focus on the relative roles of avalanching versus ripple migration. Our study of sedimentary structures in layers directly above pinstripes show that reverse size grading (an indicator of avalanche deposits) is common but not universal. This suggests that avalanching cannot be the only process involved in their formation. After storms patches of dark sand are often visible on contemporary dune surfaces and have been observed in places where sand avalanches are unlikely or impossible. These patches are invariably rippled. Dark sand is visible in ripple troughs but also extends beneath the crests in a continuous layer. Kinetic sieving during wind ripple migration appears to play an important role in pinstripe formation on Lake Michigan dunes.

The Chronology of Dune Growth and Migration in the Grand Marais Embayment, Southeastern Shore of Lake Michigan. Sean Derby, Hope College, Department of Geological and Environmental Sciences, Holland, MI 49423

The geomorphic history of the dunes in the Grand Marais Embayment (including Warren Dunes State Park) were the subject of a classic study by Tague (1946), who assigned ages to dunes based on their position in the landscape. We used radiocarbon ages from dune paleosols and OSL ages from sands below dune surfaces to construct a chronology of dune growth and migration for the same area. Tague assigned the easternmost back dune ridge to the Glenwood stage and the westernmost ridge to the Algonquin stage of ancestral Lake Michigan. The eastern ridge gave a poorly defined OSL age of 11930-9050 YBP broadly consistent with the Algonquin stage, but an OSL age of 4400-3260 YBP from the eastern most ridge implies stabilization after the Nipissing peak (~6000 YBP) in lake levels. Tague suggested a Nipissing age for massive parabolic dunes west of the back dunes. However, both radiocarbon and OSL ages suggests the growth and migration of these dunes between roughly 4500 and 2000 YBP. A relatively well developed paleo-inceptisol may indicate a period of relative dune stability in the large parabolic dunes closest to the lake beginning at roughly 2,000 YBP and ending between 600 and 300 YBP.

Using Geomorphology and Sedimentology to Reassess the Lower St. Joseph River in Southwestern Michigan. Kevin A. Kincare, DEQ, Michigan Geological Survey, Lansing, MI 48909-7756

The classic interpretation of the entrance of the St. Joseph River into the Lake Michigan basin maintains the event occurred when the glacier retreated from the Valparaiso moraine to the Lake Border moraine; i.e. the beginning of Glenwood I phase of glacial Lake Chicago. While ice stood at the Valparaiso moraine blocking drainage to the Lake Michigan basin, the St. Joseph River drained southwest to the Kankakee River through South Bend, Indiana. Terrace deposits below Berrien Springs, Michigan were considered to represent the Glenwood delta of the St. Joseph River. Recent studies show that the terrace below Berrien Springs is fluvial until it becomes deltaic in Benton Harbor, Michigan. This delta is at the elevation of the younger Calumet phase of Lake Chicago. Fieldwork also found clast-supported gravel deposits in the upper terrace flanking the river from Niles, Michigan to the river's mouth at Benton Harbor. The terrace has a single gradient traceable all the way to the Calumet delta. The clast-supported gravel represents the consolidation of drainage that probably occurred during final melting out of ice-marginal kettle chains allowing stream piracy to proceed between Niles and South Bend. Field evidence shows this did not occur until the Calumet phase.

Field Relationships between Lake Michigan Lobe End Moraines and Glacial Lake Chicago Sediments in Southern Muskegon County, Michigan. Patrick M. Colgan, Grand Valley State University, Department of Geology, Allendale, MI 49401

Geologic mapping of glacial, lacustrine, and fluvial sediments in southern Muskegon County, Michigan reveals the relationship between advances of the Lake Michigan lobe and stages of Glacial Lake Chicago at the end of the last glaciation. Surface exposures in end and ground moraines of the Lake Border advance generally contain basal till. Lacustrine sand and silt underlies and overlies this till demonstrating that glacial lakes were present before and after these advances. Wave-cut shorelines eroded in end moraines record the maximum elevation of Glacial Lake Chicago as approximately 205-208 meters above sea level. Reddish brown till is exposed in a low-relief end moraine that extends south of the City of Muskegon. This till was deposited during the Port Huron advance and is interbedded with and buried by lacustrine sand and silt. Sand and gravel 5 to 50 meters thick overlies laminated silt and clay in most of the area. A coarsening upward sequence in Glacial Lake Chicago sediments probably reflects filling of the basin with sediment both from the Muskegon River watershed and sediment from the terminus of Lake Michigan lobe during the Port Huron advance.

Origin of Small Lakes in a Coastal Dune Complex Southwest of Holland, Michigan. Elliott Eisaman, Hope College, Department of Geological and Environmental Sciences, Holland, MI 49423

Gilligan and Kelly Lakes are small lakes (< 0.1 km2) less than 1 km from Lake Michigan where westward flowing streams encounter the inland edge of coastal dunes and are diverted northwards. Four cores were obtained by vibracoring from Gilligan and one core from Kelly Lake. Twenty-one radiocarbon ages were obtained from terrestrial plant fragments within these cores. A core from Gilligan encountered a soil profile, at an elevation of ~182 meters overlain by aquatic sediment deposited during the Nipissing peak in Lake Michigan water levels. Aquatic sedimentation at Kelly began 1,000 years earlier at an elevation of ~175 meters. The lower portions of all cores are dominated by sand while carbonaceous organic sediment becomes dominant higher up. This change in the sediments coincides with a decrease in sedimentation rate and the growth of the adjacent dunes. Early sedimentation probably represents aggradation in response to estuarine back flooding of westward flowing rivers during the rise in the Lake Michigan water levels from the Chippewa low to the Nipissing high. Later growth of the coastal dunes dammed the mouths of these drowned valleys diverting the drainage and creating small lakes in which predominantly organic sediments accumulated.

A Mid-Holocene Submerged Conifer Forest in the Southern Lake Huron Basin.

R. Douglas Hunter, Oakland University, Department of Biological Sciences, Rochester, MI 48309-4476; Irina P. Panyushkina, University of Arizona, Laboratory of Tree-Ring Research, Tucson, AZ 85721; Steven W. Leavitt, University of Arizona, Laboratory of Tree-Ring Research, Tucson, AZ 85721; Alex C. Wiedenhoeft, USDA Forest Products Laboratory, Center for Wood Anatomy Research, Madison, WI 53726-2398; John Zawiskie, Wayne State University, Department of Geology, Detroit, MI 48202, Cranbrook Institute of Science, Bloomfield Hills, MI 48303

Remains of a Holocene drowned forest in southern Lake Huron were discovered in 12.5 m of water (164 m above sea level) 4.5 km east of Lexington, Michigan USA (Sanilac site). Thus far, divers have explored approximately 3 hectares characterized by patchy wood debris and occasional stumps. The forest was comprised primarily of conifers, dominated by cedar (Thuja, 50%), and hemlock (Tsuga, 20%). This community most closely matches the characteristics for rich conifer swamp (= cedar swamp). Radiocarbon ages of 20 samples range from 7,095[+ or -]50 to 6,420[+ or -]70 [.sup.14.C] yr B.P. (c. 7,935 to 7,320 cal yr B.P.). Dendrochronological analysis indicates the tree rings were formed in a stressful environment with highly variable weather conditions. We developed two floating sequences of cross-dated tree rings with no cross-dating between these two sequences suggesting the possibility of two different stands with different absolute ages. These dates provide evidence of a rich conifer swamp in existence at 6,420 [.sup.14.C] yrs BP at an elevation of 164 m a.s.l. This date establishes that a rising Lake Huron had not yet re-opened the Port Huron/St. Clair River outlet before that time and agrees with literature estimates that such drainage began about 6,000 yrs BP.

Reconstructing Paleoenvironments of Two Inland Lakes on Michigan's West Coast. B.L. Fussell, T.G. Fisher, M.J. Camp and B.B Curry, University of Toledo, Earth, Ecological and Environmental Sciences, Toledo, OH 43606

The reconstruction of paleoenvironments, specifically climate change, may be determined by studying marl horizons deposited at times of known climate variability. Several lacustrine cores from Silver and Stony Lakes, Oceana County, MI were obtained by vibracoring for the purpose of determining if there was climate variability recorded during the Little Ice Age, the hypsithermal episode, the 8.2ka event and the Younger Dryas cold period. Lab analysis consisted of [.sup.14.C] dating of wood in cores to determine marl deposition rates, description of sediment type, molluscan identification, and isotopic analysis using a Finnigan MAT 252 Mass Spectrometer. The molluscan fauna provides a good insight into the paleoecology at the time of formation, specifically proxies for water temperature, depth, turbulence, salinity and other environmental parameters. Isotopic analysis provided an accurate record of parameters such as, water temperature and salinity, which is critical when reconstructing past climates. Preliminary results showed Stagnicola sp. was only present in the older marl horizon from Silver Lake, dated at 9490 [.sup.14.C] yr B.P. and Pisidium sp., typical of low turbulence, increased over time. These preliminary results suggest Silver Lake levels were lower and possibly experienced dry periods throughout the year, compared to the turbulent lake of today.

Late Pleistocene Stable Isotope Record of Northern India Lacustrine Sediments. Steven Beukema and R.V. Krishnamurthy, Western Michigan University, Department of Geosciences, Kalamazoo, MI 49008; Navin Juyal and Ashok Singhvi, Physical Research Laboratory, Planetary and Geosciences Division, Ahmedabad, India

We present a record of [delta][.sup.13.C.sub.inorganic], [delta][.sup.18.O], [delta][], and C/N ratios obtained from lacustrine sediments from a 25 meter exposure of a relict lake in the Himalaya of Northern India. The chronology has been preliminarily defined by OSL dates ranging from 16 ka to 11 ka YBP. C/N ratios are low (<8) for the entire core, suggesting that organic material in the lake was derived from aquatic plants. Values of [delta][.sup.13.C.sub.arganic] average approximately -24% throughout the samples, which suggests that organic carbon material was derived from aquatic C3 plants during this interval. Values of [delta][.sub.18.O] show an overall increasing trend from -15% to -10%. The data suggest two major climatic periods with unique isotopic signatures. The first period extends from ~16 ka to ~14 ka, during which time the lake received a decreasing contribution of glacial meltwater. The second period, from ~14 ka to ~11 ka, is characterized by several abrupt oscillations. Values of [delta][.sup.13.C.sub.inorganic] become abruptly more positive during the first climatic period, suggesting a high nutrient input leading to high productivity during the first climatic period. A decrease in nutrient input can be attributed to a decrease in glacial meltwater and a strengthening of the Southwest Indian Monsoon.

An Elementary Model of the Earth's Magnetic Field. Jeanie I. Crone and Bradley J. Roth, Oakland University, Department of Physics, Rochester, MI 48309

Many students in a high school or university introductory physics class find the subject of geomagnetism fascinating. Instructors, however, often have a difficult time introducing this topic at an elementary level. This presentation is particularly intended for instructors in this field. It will attempt to show a simplified model of the combination of the Earth's magnetic and electrical fields into a self-sustaining geodynamo. There are three problems from introductory that can be used to demonstrate this model: the magnetic field in a solenoid; the force acting on a current in a magnetic field; and the motional EMF produced in a moving wire. These can be put together to provide a magnetic field produced by the motion of the wire, with no battery or permanent magnets present. Although this model is by no means complete, based on current data it does not refute certain findings, such as magnetic reversals.

Experimental Investigation of Antibiotic Adsorption in Sand-Iron Systems. Theresa A. O'Meara, Jonathan W. Peterson and Michael D. Seymour, Hope College, Department of Geological & Environmental Sciences and Chemistry, Holland, MI 49423

A need exists for experimental data on the fate and transport of antibiotics in aquifer materials. Experiments were performed to determine the adsorption of cephapirin (a widely-used veterinary antibiotic) on various size sands, kaolinite clay and native iron filings of various grain sizes. Two types of sand were investigated. The first was nearly pure quartz filter sands separated into 14 sieved fractions ranging from 3.35 mm to 0.30 mm diameter, with soil organic matter (SOM) ranging from 0.078-0.395 wt.%. The second was a Lake Michigan dune sand separated into 4 sieved fractions from less than 0.30 mm to 0.06 mm diameter, with SOM contents from 0.356-0.745 wt.%. This sand consisted of about 12 common rock-forming minerals, but was dominated by quartz, K-feldspar and plagioclase. Cephapirin concentrations were determined by LC/MS. Distribution coefficients (Kd's) determined for sands are 2-3 orders of magnitude smaller than Kd's determined in previously published studies of tetracycline adsorption to clays. Adsorption to kaolinite is 10 times greater than the highest Kd measured for sand. Kd's for various size iron filings are at least 1000 times greater than the highest adsorption in sand. Sand-iron mixtures, including elemental iron, hematite and magnetite are currently being investigated.

Arthropod Occurrence in a Shallow Coastal Michigan Aquifer. Eric M. Johnson, Carrie J. Thomason, Jennifer L. Cencer, and Jonathan W. Peterson, Hope College, Department of Geological & Environmental Sciences, Holland, MI 49423

Folsomia candida (Fc) is a soil arthropod occurring in leaf litter or shallow soils and is found globally. Fc is used in toxicity studies of metals, herbicides, fungicides and various insecticides. Fc occurrence in groundwater is uncommon to rare, or is under-reported in the literature. This presentation reports on Fc occurrence in some wells, but not others in the study area. Soil borings were taken from surface to water table in close proximity to wells with abundant Fc, and wells with few to no insects. Composite samples (3-15 cm thick) collected from the water table to 1 meter above the water table, were processed by standard methods. Effective grain size ([d.sub.10]), median grain size ([d.sub.50]) and uniformity coefficient ([d.sub.60]/[d.sub.10]) were determined for each composite. Variable packing relationships were used to estimate the pore volume available compared to the average body volume of Fc. Findings indicate that small differences in representative grain size ([d.sub.10] or [d.sub.50]) can determine feasibility of Fc occupancy, but do not accurately explain Fc's presence or absence. A positive relationship was found to exist between length of screen above water table and Fc abundance, indicating that Fc enters the wells from the unsaturated zone.

The Michigan Academy's Early Glacial Geology Tradition: Frank Leverett, Frank Taylor, Stannard Bergquist and Others. Diane K. Baclawski, Michigan State University, Geology Library, East Lansing, MI 48824-1115

The Michigan Academy of Science, Arts & Letters has been an important communication medium for glacial studies during the last century. Frank Leverett and Frank Taylor, well known for their contributions to glacial studies in the Michigan Basin, were both frequent contributors to the meetings of the Academy. There are many references to the Academy in the Leverett-Taylor Archive at Michigan State University. Both Leverett and Taylor prepared presentations for the Academy meetings. Other Glacial Geologists have also contributed to the Academy's glacial tradition, including W. H. Hobbs, J Harlan Bretz, Jethro Veatch, E.C. Case, Stannard Bergquist, and Israel Russell. Bergquist is particularly notable. As Leverett's grad student and later Head of the Dept. of Geology and Geography at MSC (MSU), Bergquist continued the legacy of glacial studies well into the mid-century. Both Leverett and Bergquist also served as presidents of the Academy.
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Publication:Michigan Academician
Geographic Code:1USA
Date:Jan 1, 2008
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